And in the second or so that it takes you to say that, Data would be able to pick up some lose bit of equipment and throw it at Fajo's head to knock him unconscious.

Data's reflexes are certainly fast enough.

Or there was no loose equipment around. Or there was, but it was all either too light to knock Fajo out or too heavy to avoid killing him. Can't throw the disruptor because they're very unstable (wouldn't you know).

Why not? Guinan once fired an energy weapon at the ceiling in Ten Forward. And there have been lots of other times people have fired energy weapons at bulkheads on ships.

None of them were Varon-T disruptors, though. They're special and it would be incredibly dangerous.